In the latest article in an online magazine used by the Islamic State for propaganda and recruitment, the terror group has reportedly told jihadists to kidnap non-Muslims children in the United Kingdom.

According to the Sun, the detailed and instructional article in Rumiyah magazine is accompanied by a picture of young boys from King's College Choir in Cambridge with the caption: "It is permissible to kidnap the children of the Harbi Kuffar (non-Muslims)."

Islamic State militants are currently battling Syrian army backed by heavy Russian air strikes to defend their remaining territory in the country. In the past, they have used kidnapping as a tactic. The abducted children are kept as slaves, used as human shields during battles and also trained to be suicide bombers.

According to a study by the Financial Action Task Force, ISIS's five primary sources of revenue also includes kidnapping for ransom.

"If he (a Muslim) kidnaps them (non-Muslim) or their children, or subdues them in any way, then the lives and wealth of the harbi kuffar (non-Muslims) are permissible... they own them," the Sun quoted the article as saying.

The article also calls on those "residing in the lands of the kuffar (non-Muslims)" to steal their wealth.

"Do not forget that their war on the Islamic State is dependent on wealth, so purify your intentions, place your trust in Allah, and do not seek anyone's advice with regards to taking their wealth," it added.

Propaganda video shows ISIS training children to be
Militant Islamist fighters take part in a military parade along the streets of northern Raqqa province in June. ISIS is training children to build next generation of Jihadis.Reuters

Rumiyah was first published in September 2016 and is released in several languages, including English, French, German, Russian, Indonesian and Uyghur. The name Rumiyah (Rome) is a reference to a Hadith in which the Prophet Muhammed said that Muslims would conquer both Constantinople and Rome, in that order.